needless_collect: Lint LinkedList and BinaryHeap in direct usage.

Those two types are supported already when used indirectly.
This commit adds support for direct usage as well.

Author: mgacek8

clippy_lints/src/loops/needless_collect.rs

@@ -31,7 +31,9 @@ fn check_needless_collect_direct_usage<'tcx>(expr: &'tcx Expr<'_>, cx: &LateCont
             let is_empty_sugg = Some("next().is_none()".to_string());
             let method_name = &*method.ident.name.as_str();
             let sugg = if is_type_diagnostic_item(cx, ty, sym::vec_type) ||
-                        is_type_diagnostic_item(cx, ty, sym::vecdeque_type) {
+                        is_type_diagnostic_item(cx, ty, sym::vecdeque_type) ||
+                        is_type_diagnostic_item(cx, ty, sym::LinkedList) ||
+                        is_type_diagnostic_item(cx, ty, sym::BinaryHeap) {
                 match method_name {
                     "len" => Some("count()".to_string()),
                     "is_empty" => is_empty_sugg,

tests/ui/needless_collect.fixed

@@ -2,7 +2,7 @@
 
 #![allow(unused, clippy::suspicious_map, clippy::iter_count)]
 
-use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
+use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList};
 
 #[warn(clippy::needless_collect)]
 #[allow(unused_variables, clippy::iter_cloned_collect, clippy::iter_next_slice)]
@@ -24,4 +24,13 @@ fn main() {
     sample.iter().collect::<HashSet<_>>().len();
     // Neither should this
     sample.iter().collect::<BTreeSet<_>>().len();
+
+    sample.iter().count();
+    sample.iter().next().is_none();
+    sample.iter().cloned().any(|x| x == 1);
+    sample.iter().any(|x| x == &1);
+
+    // `BinaryHeap` doesn't have `contains` method
+    sample.iter().count();
+    sample.iter().next().is_none();
 }

tests/ui/needless_collect.rs

@@ -2,7 +2,7 @@
 
 #![allow(unused, clippy::suspicious_map, clippy::iter_count)]
 
-use std::collections::{BTreeMap, BTreeSet, HashMap, HashSet};
+use std::collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList};
 
 #[warn(clippy::needless_collect)]
 #[allow(unused_variables, clippy::iter_cloned_collect, clippy::iter_next_slice)]
@@ -24,4 +24,13 @@ fn main() {
     sample.iter().collect::<HashSet<_>>().len();
     // Neither should this
     sample.iter().collect::<BTreeSet<_>>().len();
+
+    sample.iter().collect::<LinkedList<_>>().len();
+    sample.iter().collect::<LinkedList<_>>().is_empty();
+    sample.iter().cloned().collect::<LinkedList<_>>().contains(&1);
+    sample.iter().collect::<LinkedList<_>>().contains(&&1);
+
+    // `BinaryHeap` doesn't have `contains` method
+    sample.iter().collect::<BinaryHeap<_>>().len();
+    sample.iter().collect::<BinaryHeap<_>>().is_empty();
 }

tests/ui/needless_collect.stderr

@@ -30,5 +30,41 @@ error: avoid using `collect()` when not needed
 LL |     sample.iter().map(|x| (x, x)).collect::<BTreeMap<_, _>>().is_empty();
    |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
 
-error: aborting due to 5 previous errors
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:28:19
+   |
+LL |     sample.iter().collect::<LinkedList<_>>().len();
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `count()`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:29:19
+   |
+LL |     sample.iter().collect::<LinkedList<_>>().is_empty();
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:30:28
+   |
+LL |     sample.iter().cloned().collect::<LinkedList<_>>().contains(&1);
+   |                            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `any(|x| x == 1)`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:31:19
+   |
+LL |     sample.iter().collect::<LinkedList<_>>().contains(&&1);
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `any(|x| x == &1)`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:34:19
+   |
+LL |     sample.iter().collect::<BinaryHeap<_>>().len();
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `count()`
+
+error: avoid using `collect()` when not needed
+  --> $DIR/needless_collect.rs:35:19
+   |
+LL |     sample.iter().collect::<BinaryHeap<_>>().is_empty();
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `next().is_none()`
+
+error: aborting due to 11 previous errors